Ok I 'm not sure how to adequately word my question, but why is it that FM radio stations always end in odd numbers, i.e. 102.3, 97.1, 104.9, etc etc.
What’s the reasoning?
IANA Engineer, but they don’t - it just appears that way.
Lots of radio stations here in Dublin are normal “big” licenced stations like “98FM”, “FM104” (which actually resides at the wavelength of its previous incarnation, 104.4), 101FM, 102FM… and so on.
What you are thinking of is the small unlicenced “pirate” stations - that can’t afford all the hugely expensive equipment, and so can only broadcast over a tiny wavelength.
This means that a big station could afford to occupy all wavelengths between 100FM & 101FM (which makes it easier for listeners to find), but the small stations have to make do with a 10th of that e.g. 102.1 - ten times smaller and much harder for a listener to find.
Hope that helps.
No, these are major radio stations owned by giant corporations. I am in America though so maybe things are different over here.
The straight dope from the Federal Communications Commission:
Sorry, Decimal Number.
Similarly AM frequencies are separated by 10 kHz, so all radio station frequencies are multiples of 10. Except in Japan where stations are separated by 9 kHz, which causes a compatibility problem with digital tuners. The American Armed Forces Radio in Tokyo uses 810 kHz (divisible by both 9 and 10) to avoid this problem.
Yes, all FM station frequencies end in an odd decimal as indicated by Walloon’s link. This rule does NOT hold in Europe. I am not sure of the regulations here, but in Germany we have stations with odd and even decimal numbers.
This cause no end of trouble for American’s in the US Armed Forces. Many radios intended for use in the US cannot tune to the even decimals - which results in poor reception of some of the AFN radio stations.
Ah, thought it was just an American thing. The big independent station in London (Capital FM) is at 95.8, and there are many many more.
Similarly, the AM frequencies (or “medium wave” as older folk call it) in the UK are multiples of 9 (eg BBC Radio 5 is at 909 and 693).
Arrgghh! I madre another apostrophe s for a plural. Somebody shoot me, please!
True. Both of our cars were bought in Texas, and have radios which only tune to odd decimals. This makes changing and seeking channels while driving a real bitch, since most channels that I listen to in Helsinki have frequencies which end in even decimals. No surfing the waves to see if there’s anything good on for me, oh no. I just tune the radio onto one station before heading out and pray they won’t play N’Sync. 
So, if US FM stations are allocated twice the bandwidth of their European counterparts, does that mean that FM radio sounds better in the States than it does here?
Possibly, but I think the fact that European radios have finer tuning goes some way to counteract this. Most decent radios with digital tuning are adjustable to 0.05MHz - you often find that you get better reception at, say, 97.75MHz rather than the “official” 97.7, because this minimises interference from another station on a nearby frequency. The idea of only being able to tune to 0.2MHz sounds a bit ropy to me. YRMV.
Greater bandwidth always equals better sound. Your tuning theory is rather fanciful, because the allocated bandwidth is VERY carefully regulated so nobody steps on each other’s frequencies, except right in the very fringe where one frequency ends and one begins. The center frequency is where you get max FM deviation.
The interference you speak of is not from another station. If it were, they would be paying a hefty fine.
The Europeans use the same bandwidth that the US does - they just distribute it differently.
As for having tuning finer than .1MHz, it is only useful if the frequency generator (the tuner) in your radio is out of whack. It should be accurate enough that you only need to tune to 0.2MHz (US) or 0.1MHz (European.) If it isn’tthat accurate, then you may need to tune a little above or below.
An American radio in Europe may get interference from another station that a European radio wouldn’t. The frequencies are distributed based on how far you expect the signal to be received. That is, you take the transmit power of the station and the expected sensitivity of the receiver and estimate the broadcast coverage. Two stations that are spaced further apart than the expected broadcast range can have the same or very close frequencies without interference.
If, however, the receiver is much more sensitive than planned (or the transmitter more powerful - which will get you in a world of trouble,) then you can get interference. This happens quite a bit with American radios. They are designed to be more sensitive than the radios for the European market, and consequently sometimes receive from two stations even though they should (by the planner’s calculations) be out of range of one or the other - or even both.
As a rule, a European market radio with a digital synthesizer tuner will tune to 0.1MHz, and a US market radio with a digit synthesizer tuner will tune to 0.2MHz. A radio with a varactor tuner and a digital display that works from the tuning voltage will display out to 0.05 MHz, and you may have to tune off of the official frequency to get good reception. This is because the display is inaccurate, not because the station is at the wrong frequency.
I forgot that point, Mord. Thanks.